Result: standard mapping
How many DS0s are in an E2?
An E2 carries 120 DS0s, per ITU-T G.702 and ITU-T G.704.
120
DS0s in an E2
Working
E2 → 4 × E1 → 30 × E0 → 1 × DS0
- 4 × E1 in each E2 ITU-T G.702Four E1s.
- 30 × E0 in each E1 ITU-T G.70430 voice channels in 32 timeslots. TS0 is framing and TS16 is channel-associated signalling.
- 1 × DS0 in each E0 ITU-T G.702E0 and DS0 are each one 64 kbit/s PCM channel.
- 4 E1s
- 4 × 30 = 120 E0s
- 4 × 30 × 1 = 120 DS0s
Leftover capacity
768 kbit/s of each E2 line rate (8.448 Mbit/s) sits outside 120 × 64 kbit/s of DS0 line rate (7.680 Mbit/s). That remainder is overhead, fixed stuff or justification. It is not another whole tributary.
By bit rate only
Dividing the line rates gives 132, which floors to 132 DS0s by bit rate only. The standard mapping is 120. Use the mapping.